JP4762469B2 - Prevention of oil backflow from screw compressor in refrigeration chiller. - Google Patents

Description

[0001]
Background of the invention The present invention relates to a screw compressor. In particular, the present invention relates to a screw compressor used for a freezing chiller. More particularly, the present invention relates to preventing back flow of oil from a screw compressor in a refrigeration chiller and resulting oil drop to the evaporator of the system.
[0002]
The screw compressor is a compressor in which two or more screw rotors are arranged so as to mesh with each other in a working chamber. As the screw rotors rotate in reverse, the gas flows into the working chamber at the first relatively low pressure, the gas is compressed in the working chamber, and the gas is discharged at a high pressure called discharge pressure therefrom. .
[0003]
In many screw compressor applications, including refrigeration chiller applications, it is possible to inject oil directly into the compressor's working chamber for cooling and sealing. In addition, oil is used to lubricate the bearings of the compressor. Oil used as bearing lubricating oil in a refrigeration chiller is usually sent to a position in the compressor where the pressure of the refrigerant gas is relatively low. Therefore, such oil finally reaches the working chamber of the compressor and is entrained by the refrigerant gas flowing in the working chamber. Such oil, along with other oil injected directly into the working chamber of the compressor, is taken out of the compressor along with the flow of gas discharged from the compressor.
[0004]
The flow of the refrigerant gas discharged from the screw compressor of the refrigeration chiller contains a relatively large amount of oil, and this oil must be returned to the compressor for the above-mentioned purpose. Arranged immediately downstream of the compressor, oil is separated and collected from the flow of the discharge gas and returned to the compressor. In many chiller systems, separated oil is sent from the oil separator to the compressor by using the discharge pressure of the oil separator.
[0005]
Oil separators used in such systems generally separate oil from refrigerant gas passing through the separator with a high efficiency of 99% or more before the refrigerant gas is sent to the system condenser, but ultimately It will be understood that the compressor oil will be depleted. Generally, oil passing through the system oil separator is routed through the system condenser to the system evaporator where it accumulates on or in the liquid refrigerant present at the bottom of the evaporator. Typically, means are provided for periodically returning such relatively small amounts of oil from the system evaporator to the system compressor. In all types of frozen chillers, the transport of such oil is common, and the amount of such oil is usually very small as a proportion of the oil supplied to the chiller.
[0006]
There is a direct flow path from the chiller evaporator to the chiller compressor section (from which the suction gas is routed to the compressor), so that under certain conditions, the oil in the compressor is reversed from the compressor. Can even flow into the evaporator. If anything, such a condition is inherent to a refrigeration chiller using a screw compressor and its degree is large. This is due to the amount of oil used for various purposes in such a compressor and because the system evaporator is located below the system compressor and is generally in communication with the suction area of the compressor. This is because. The oil flow directly from the compressor to the system evaporator exceeds the processing capacity of the oil return device associated with the evaporator, although it is not common, so that the amount of oil in the correct position is insufficient and in operation When the compressor is not continuously supplied with sufficient oil, the chiller stops urgently.
[0007]
US Pat. Nos. 5,086,621 and 5,396,784 describe examples of conventional structures that receive and hold backflowed oil from a refrigeration chiller compressor and return the oil to the compressor. In US Pat. No. 5,086,621, this oil backflow problem is addressed by placing a tray in the evaporator below the piping through which intake gas is routed from the evaporator to the compressor. This tray receives any backflow oil and accumulates it there. The oil is then continuously returned to the system compressor using an eductor device.
[0008]
Similarly, US Pat. No. 5,396,784 provides a tray for receiving and returning backflow oil below the outlet of the evaporator of the refrigeration chiller. However, in the method of US Pat. No. 5,396,784, when the level of oil in the tray is sufficiently high, the flow of gas from the evaporator to the compressor is limited, thereby increasing the gas flow rate. As the flow rate of gas flowing from the evaporator to the compressor increases, the oil in the tray is entrained in the gas flow returning from the evaporator to the compressor.
[0009]
With either construction, it should be understood that the parts / assemblies that need to be built into the system evaporator need to be manufactured and installed to address the problem of oil backflow. Such parts / assembly parts, their manufacture and installation are costly and operating them increases the power consumed by the entire chiller system.
[0010]
There is a continuing need for a device that prevents backflow of oil from the screw compressor to the evaporator in a refrigeration chiller system where the additional cost of the compressor or chiller system is low and does not reduce the efficiency of the chiller.
[0011]
SUMMARY OF THE INVENTION An object of the present invention is to limit and / or prevent backflow of oil from a refrigeration chiller compressor to a refrigeration chiller evaporator.
[0012]
Another object of the present invention is that in the refrigeration chiller system, the oil that flows back in the compressor is shut off before the oil flowing out of the compressor flows out of the compressor, and the direction of the oil is changed from the compressor to the condenser. It is to prevent backflow of oil.
[0013]
It is a further object of the present invention to prevent backflow of substantially all oil from the compressor to the condenser in a refrigeration chiller system. The method is passive, with additional costs such as chiller manufacturing costs, cost of parts / assembly parts used to prevent oil backflow, and costs due to impact on chiller operating efficiency being relatively low. Yes.
[0014]
The above and other objects of the present invention will become apparent from the accompanying drawings and the preferred embodiments described below. In the preferred embodiment and the accompanying drawings, a refrigeration chiller system using a screw compressor is shown. The screw compressor primarily includes an upstream and / or suction area of the compressor's working chamber to prevent oil from escaping from the compressor housing, to block backflowing oil and to change its direction back to the compressor. One or a plurality of oil backflow prevention baffles are systematically disposed upstream of the first and second oil baffles. In the preferred embodiment, such a baffle is disposed in the compressor housing portion in which the compressor drive motor is located. In the preferred embodiment, the drive motor is cooled utilizing a refrigerant gas flow from the system evaporator to the compressor working chamber. Under relatively chiller operating conditions where oil backflow from the compressor to the evaporator can occur without the baffle being placed, the baffle blocks oil backflow from the compressor housing for use in the compressor. Change the direction to the upstream direction.
[0015]
DESCRIPTION OF PREFERRED EMBODIMENTS Referring first to FIG. 1, the most basic form of refrigeration chiller 10 includes a compressor 12, a condenser 14, an expansion device 16, and an evaporator 18, and includes a refrigerant circuit. All of them communicate to form In general, the refrigerant gas is compressed by the compressor 12 and discharged from the compressor at a relatively high pressure and high temperature. This gas is sent to the condenser 14 where it is cooled and condensed by exchanging heat with a relatively cool refrigerant such as water flowing in the tube bundle 20.
[0016]
The condensed refrigerant flows from the condenser 14 to the expansion device 16 and passes through the expansion device 16, whereby the pressure and temperature of the refrigerant are reduced. A part of the liquid refrigerant passing through the expansion device 16 is vaporized in the expansion process. The two-phase refrigerant flows from the expansion device 16 to the evaporator 18 where it contacts the medium flowing in the tube bundle 22 and exchanges heat.
[0017]
The medium flowing through the tube bundle 22 in the evaporator 18 retains heat from the heat load. The purpose of the chiller 10 is to cool the medium that retains the heat. This heat is given to the relatively low temperature and low pressure refrigerant flowing into the evaporator 18 from the medium, whereby most of the liquid phase of the refrigerant is vaporized. The cooled medium flowing through the tube bundle 22 is returned to the heat load to cool the heat load. At the same time, the refrigerant evaporated in the evaporator 18 returns to the compressor 12 where it is compressed and sent to the condenser and the process continues.
[0018]
In the preferred embodiment of the chiller system of the present invention, the compressor 12 is a screw type compressor. The compressor 12 generally has a housing 24 that includes a rotor housing 26 and a motor housing 28. The rotor housing 26 defines a working chamber 30 in which a first screw rotor 32 and a second screw rotor 34 that mesh with each other and rotate counterclockwise are disposed. The compressor drive motor 36 is disposed in the motor housing 28 and is connected to one of the rotors 32 and 34 to drive it.
[0019]
In the preferred embodiment chiller, intake gas is routed from the evaporator 18 via an intake line 38 that opens to the motor housing portion 28 of the compressor housing 24. The intake gas flows around the motor 36 through the motor housing 28 and cools the motor 36 in the process. Next, the suction gas is sucked into the working chamber 30, compressed by the reverse rotation of the motor-driven screw rotor, discharged from the discharge line 40 as described above, and reaches the condenser 14 through the oil separator 42.
[0020]
As with most compressors, in the preferred embodiment screw compressor 12, one or more of the compressor elements are rotating parts, usually attached to a bearing. In general, such a bearing requires lubricating oil. In the preferred embodiment chiller system, the screw rotors 32 and 34 are attached to bearings for rotation, and such bearings 44 and 46 require lubricating oil. Since the compressor 12 is a screw compressor, oil is required for another purpose. These other purposes include cooling of the compressed refrigerant gas and / or cooling of the screw rotor in the working chamber, sealing between rotating screw rotors, and sealing of the rotor and wall of the working chamber 30. It is.
[0021]
With reference to the above and referring to FIG. 2, the chiller 10 requires a large amount of oil to be sent to the bearings 46 and 44 via supply lines 48 and 50, for example. The oil is injected into the working chamber 30 of the compressor 12 through the supply line 52. The supply line 52 is open toward a portion where the pressure of the refrigerant gas being compressed in the working chamber 30 is lower than the discharge pressure.
[0022]
This oil is sent from the oil reservoir 54 to the supply lines 48, 50, and 52 through the line 56 due to the discharge pressure applied to the oil separator 42. The pressure of this oil is higher than the pressure in the part where the oil is used and / or the part where the oil is induced / released / exhausted after being used for a given purpose in the compressor. Since the efficiency of the oil separator 42 is high, a relatively small amount of oil discharged from the compressor 12 is entrained in the discharged refrigerant gas, and is sent to the evaporator 22 through the oil separator together with the refrigerant gas. A relatively small amount of such oil is returned via line 202 by device 200, shown in phantom in FIG. 1, for use in the compressor.
[0023]
The portion where the oil is sent after being used in the compressor also includes the compressor suction area 58. Under normal operating conditions, the flow of gas passing through and passing through the compressor 12 is sufficiently high in pressure, and the oil in and near the suction region 58 is entrained by the fluid gas and into the compressor's working chamber. It is inhaled and sent to the oil separator 42 via the inhalation. For load conditions where the amount of gas flowing from the evaporator into the compressor is significantly reduced, the compression is driven by the dynamics of the rotation of the drive motor and screw rotor in the compressor housing and the pressure pulsation generated under such conditions. Oil blows out of the machine suction area 58 and is returned to the system evaporator through the motor housing against the relatively weak gas flow from the evaporator to the compressor. Under certain conditions, such an oil back-flow force is sufficiently strong and sustained so that a relatively large amount of oil supplied to the compressor flows back from the compressor to the system evaporator. In general, the amount of oil that flows back and returns exceeds the amount that the oil return device 200 returns the oil to the compressor in a timely manner. If such a situation cannot be dealt with, the compressor will stop urgently and / or Damage due to lack can occur.
[0024]
Still referring to FIGS. 3 and 4, the flow of suction gas from the evaporator 18 through line 38 reaches the motor housing 28 as indicated by arrow 100 in the preferred embodiment. When it reaches the motor housing, it passes over and around the motor 36 and the process cools the motor. Part of the intake gas flow passes through a relatively small rotor stator gap (not shown) of the motor, and in a preferred embodiment, intake gas paths 60A, 60B, and 60C formed in the inner wall of the motor housing. More fluid passes through and around the motor 36. As it passes through the drive motor, the intake gas reaches an intake area 58 defined at a generally boundary position between the rotor housing and motor housing portion of the compressor housing 24. From there, the suction gas is sucked into the working chamber of the compressor.
[0025]
When the compressor 12 is at the maximum load, as illustrated in FIG. 2, the slide valve 62 abuts against the slide stopper 64, whereby all the suction gas flowing into the suction region 58 is oriented and the suction sub-area 58A. Flows in. The suction sub area 58A is located at the suction port of the compressor. The suction port is a position where gas exits the suction area of the compressor and is sucked into the working chamber. The suction gas flowing into the working chamber of the compressor through the suction port is compressed in the working chamber and supplied to the oil separator 42 through the discharge line 140 from the compressor. Under the maximum load condition, the flow rate of the suction gas is generally large and the flow velocity is large, and as will be described in detail below, oil such as oil in the oil reservoir 66 is entrained with the gas and sent to the sub-area 58B of the suction region 58. .
[0026]
When the chiller 10 is operating at a lower load than the maximum load, the slide valve 62 contracts away from the distance slide stopper 64 corresponding to the chiller load, thereby causing a portion of the working chamber 30 and the screw rotor therein. Is exposed to the suction region 58A, whereby a part of the refrigerant gas flowing in the working chamber is effectively shortcutted. When the slide valve contracts, the effective length of the screw rotor is shortened, thereby reducing the capacity of the compressor. In the case of the compressor 12, when the slide valve 62 contracts, the screw rotors that mesh with each other and rotate in the reverse direction are exposed to the sub-area 58B of the suction region 58 of the compressor. The suction sub-area 58B is normally located at the bottom of the compressor opposite the suction sub-area 58A and is the part where the oil is collected after being used for various purposes by the compressor as shown. .
[0027]
Although contraction of the slide valve 62 away from the slide stopper 64 is common and often occurs, it changes the flow pattern of the suction gas in the suction area of the compressor. Further, when the slide valve 62 contracts away from the slide stopper 64, the screw rotor rotating at high speed is exposed to the oil reservoir 66 that accumulates in the suction sub area 58B. The amount of this oil is considerable but depends on the operating conditions. Under most operating conditions, the oil flows continuously into and out of the oil reservoir 66 due to the flow of the suction gas, and even when the slide valve is contracted, the oil flows through the working chamber along with the gas flow. Sent to the separator.
[0028]
However, as described above, when the chiller is operating, particularly when the slide valve 62 is completely or almost completely contracted, the oil in the suction area 58 including the oil in the oil reservoir 66 is compressed against the flow of the suction gas. The machine 12 can back flow into the system evaporator. Conventional structures have been addressed by the receipt and / or collection of such oil in the system evaporator or using equipment designed to return such oil from the system evaporator back to the compressor. However, the chiller of the preferred embodiment of the present invention first provides a method for preventing oil backflow from the compressor housing.
[0029]
Accordingly, one or more baffles are systematically arranged upstream of the working chamber 30 of the compressor housing 24. The position is a position that prevents and / or physically obstructs and / or redirects the majority of any oil that flows back into it. However, such baffles have no effect on the normal flow of gas into the compressor working chamber, i.e. do not impede flow. In the preferred embodiment, the first baffle 68 is located generally at the end of the motor housing 28 closest to the suction line 38. The first baffle 68 includes a generally planar wall 70 that faces the downstream flow of gas into the intake gas path 60A. The wall 70 does not impinge on the wall 70 the intake gas that normally flows downstream through the compressor housing 24 and is not obstructed in any other way, but the wall 70 flows back through the path 60A with respect to the suction line 38. It acts as a collision surface for all the oil flows that do.
[0030]
Some oil escapes the baffle 68 and flows upstream from the compressor to the evaporator, but in most cases the amount is in the processable range. In addition, a relatively small amount of oil can be returned to the compressor under normal operating conditions by the device 200. The main purpose of this device 200 is to return a relatively small amount of oil that flows downstream in the normal operation of the chiller and enters the evaporator.
[0031]
The oil impinging on the wall 70 of the baffle 68 flows through the wall 72 inclined by gravity and reaches the bottom of the motor housing such as the position 74. Just as the wall 72 is not generally exposed, the wall 30 is neither affected nor affected by the normal downstream flow of gas entering the motor housing and reaching the suction area 58. The oil that has reached the position 74 flows into oil return channels 76 and 78 formed at the bottom of the motor housing. These fluids 76 and 78 deliver this oil to an oil sump 66 in the suction sub-area 58B of the compressor housing. When the operating condition of the chiller is normalized, oil is sucked from the oil reservoir 66 into the working chamber of the compressor.
[0032]
In the preferred embodiment, the second baffle 80 is disposed in the compressor housing 24 between the portion of the intake gas that has exited the intake gas path 60A and flowing into the intake region 58 in the downstream direction and the lubricating oil reservoir 66. ing. In the preferred embodiment of the compressor physical structure, the screw rotors rotate in opposite directions within the compressor working chamber, the relative arrangement of the intake gas path within the motor housing, and the compressor drive motor and rotation. All the relative arrangements in the motor rotation direction 82 cooperate to allow the oil in the oil sump 66 to be conveyed upward along the surface 84 of the motor housing 28 toward the outlet of the path 60A.
[0033]
When the baffle 80 is not disposed under normal operating conditions, the lubricating oil that moves upward along the surface 84 is entrained by the suction gas present in the suction gas path 60A and is taken together with the suction gas in the operating chamber of the compressor. To be supplied. Under conditions of low load / extreme ambient temperature at the start of operation, the amount of gas flowing through path 60A is relatively small and / or the flow rate is slow, so along the surface 84 when the baffle 80 is not provided. Thus, the oil moving upward can flow back through the passage 60A against the flow of the weak suction gas flowing in the downstream direction through the suction gas passage 60A.
[0034]
By placing the second baffle 80 directly below the outlet of the motor housing path 60A, most of the oil flowing upwardly from the oil reservoir 66 along the surface 84 is indicated by the arrow 86 in FIG. In this manner, the baffle 80 blocks and deflects the direction to effectively block the oil flow to the vicinity of the outlet of the path 60A. Thus, first, the second baffle 80 effectively prevents most of the oil in the oil reservoir 66 from being sent to a position in the suction area 58 where the oil is easily blown away from the compressor housing. . One baffle 68 is disposed at a position where the oil that actually flows back through the intake gas passage 60A is blocked, and such lubricating oil flows downward at the upstream end of the motor housing and returns to the oil reservoir 66. It is formed to flow in.
[0035]
As described above, the compressor in the chiller of the present invention is a screw compressor in which two baffles are arranged, and the suction motor flows around the drive motor before entering the working chamber of the compressor. Please understand that it is designed to cool. The present invention is not only applicable to screw compressors where the compressor drive motor is upstream of the compressor and cools the drive motor with suction gas, but also without any interaction with the drive motor for cooling purposes etc. It should be understood that the present invention is also applicable to a compressor in which gas is drawn directly into the compressor's working chamber via a suction area.
[0036]
Furthermore, in the chiller compressor of the present invention, the oil present in the suction area 58 tends to be sent to a position in the suction area 58 depending on the gas hydrodynamics and the direction of rotation of the rotor. In that position, under low load / extreme ambient temperature operating conditions, oil may flow back from the compressor housing through the intake gas path 60A as opposed to another intake gas path formed in the motor housing. is there. In other words, in the chiller compressor of the present invention, the oil does not easily accumulate in a position where the oil easily flows backward from the intake gas path 60B or 60C even under conditions of low load / extreme ambient temperature. Accordingly, the baffles 68 and 80 are designed and arranged with respect to the intake gas path 60A, taking into account the compressor structure and oil backflow tendency of the preferred embodiment. Other compressors may require more or one less baffle than the preferred embodiment baffles to block and / or prevent oil backflow. Also, the position of such baffles may differ from the position of the preferred embodiment chiller compressor. It should be understood that such a structure is also within the scope of the present invention.
[0037]
Further, it should be understood that in some compressor configurations, oil return paths 76 and 78 may be eliminated. For example, referring to FIG. 3, the height of the surface 300 of the motor housing 28 that defines the intake gas path 60 </ b> C with other members is shown as an opening through which the intake gas flows into the motor housing 28, as indicated by the dashed line 302. When the height is at the lowermost end of 304 or lower, the oil at the upstream end of the motor housing can be returned to the suction area 58 via the path 60C without the need for the paths 76 and 78. Recall that path 60C is not an easy path for oil backflow from the compressor. Thus, although oil return paths 76 and 78 are essential in some cases, they may not be necessary in other cases and when the compressor structure is different.
[0038]
While the invention has been described in accordance with a preferred embodiment, other modifications, additions, variations, etc. will be apparent to those skilled in the art. Accordingly, the scope of the present invention is not limited to the structure of the preferred embodiment described above.
[Brief description of the drawings]
FIG. 1 is a schematic view of a frozen chiller of the present invention.
FIG. 2 is a cross-sectional view of a compressor portion of the refrigeration chiller of FIG.
3 is an end view of the motor housing of the compressor illustrated in FIG. 2 taken along line 3-3. FIG.
4 is a perspective cross-sectional view of the motor housing of FIG. 3 taken along line 4-4.

Claims (26)

A refrigeration chiller including a condenser, an expansion device, an evaporator, and a compressor,
The compressor, the condenser, the expansion device, and the evaporator are connected in series to form a refrigerant flow and a refrigerant path,
The compressor includes a housing, at least one baffle, a working chamber, and a position upstream of the working chamber in which oil tends to accumulate;
The at least one baffle is disposed upstream of the working chamber of the housing, the position of which is opposed to the flow of refrigerant gas in the downstream direction from the evaporator through the housing to the working chamber. A freezing chiller characterized in that it is in a position to prevent outflow from the housing.     2. The refrigeration chiller according to claim 1, wherein the at least one baffle is disposed at a position that blocks a reverse flow of oil from a position where the oil tends to accumulate in the compressor housing and changes a direction thereof.     2. The refrigeration chiller according to claim 1, wherein the direction of the oil whose direction is changed by the baffle is changed to a position where the oil is easily collected.     A compression disposed in the compressor housing, generally upstream of the working chamber, upstream of the position where the oil tends to accumulate, and downstream of the position where refrigerant gas flows into the compressor housing from the evaporator. The refrigeration chiller according to claim 3, further comprising a machine drive motor.     The refrigeration chiller according to claim 4, wherein the at least one baffle is disposed upstream of the compressor drive motor.     The compressor housing defines one or more intake gas paths generally along the length of the outside of the compressor drive motor, and the majority of the intake gas flowing into the compressor housing is the one or more Flowing into the working chamber via a plurality of suction gas passages, the at least one baffle having a surface arranged to face downstream in the at least one suction gas passage, thereby 6. The refrigeration chiller according to claim 5, wherein oil flowing in an upstream direction hits the surface and flows downward therefrom.     An upstream position of the motor where the compressor housing defines one or more oil return paths, and the one or more oil return paths flow down the surface of the at least one baffle to deposit oil; The refrigeration chiller according to claim 6, wherein a position downstream of the motor in which oil flows out of the at least one oil return path and flows to a position where the oil is likely to accumulate is communicated.     The compressor has two baffles, and a first baffle of the two baffles is arranged upstream of the motor to shut off and change the direction of oil flowing back in the compressor housing. The second baffle of the two baffles is first arranged to prevent backflow of oil from a position where the oil tends to accumulate. The frozen chiller described.     The refrigeration chiller according to claim 8, wherein the second baffle is located substantially downstream of the motor. A first screw rotor; a second screw rotor; and a capacity control valve;
The first screw rotor and the second screw rotor are disposed in the working chamber so as to rotate, and the position of the capacity adjusting valve is adjustable to change the capacity of the compressor, and the compressor 10. The first and second rotors are exposed at a position where the oil is accumulated in the compressor housing when the position of the capacity adjustment valve is adjusted to reduce the capacity of the compressor housing. The frozen chiller described in 1.     10. The refrigeration chiller according to claim 9, wherein the second baffle is arranged to block the flow of oil and change its direction so as to be away from one downstream outlet of the suction path.     The at least one baffle substantially prevents backflow of oil from a position where the oil tends to accumulate against the downstream flow of gas from the evaporator to the working chamber of the compressor. The frozen chiller according to claim 2, wherein the chiller is disposed. A compressor drive motor disposed in the housing upstream of the working chamber;
The compressor housing defines at least one intake gas path, the path extending generally along the length of the outside of the motor and upstream of the position where the oil accumulates and at that position At least in the compressor housing, and the at least one baffle allows oil flow from a position where the oil tends to accumulate to a position where the at least one intake gas path is open. 13. The chiller according to claim 12, which is arranged to prevent. A baffle disposed upstream of the motor;
2. The refrigeration chiller according to claim 1, wherein the chiller is arranged so as to change the direction of oil blown upstream through the at least one intake gas path and to return the oil to a position where it can easily accumulate. A screw compressor including a housing, a first screw rotor, a second screw rotor, and a baffle,
The housing defines a working chamber, a suction area where oil is likely to accumulate, and a position where suction gas flows into the housing;
The first screw rotor and the second screw rotor are disposed so as to mesh with each other in the working chamber, and the suction region is located at the position where the working chamber and suction gas flow into the housing. Is a position where oil is likely to collect,
The baffle is provided in the housing upstream of the working chamber but downstream of the position where suction gas flows into the housing, and the suction gas flows into the compressor housing from the suction region. A screw compressor, characterized in that it is arranged to prevent backflow of oil through the position.     A motor coupled to at least one of the first and second rotors, the motor being generally upstream of the suction region and downstream of the position at which suction gas flows into the compressor housing; The screw compressor according to claim 15, wherein the screw compressor is disposed in the outer space.     The compressor housing defines a suction gas path that communicates between the suction area and the position where the suction gas flows into the housing, and passes through the suction gas path under predetermined compressor operating conditions. 17. The screw compressor according to claim 16, wherein the oil tends to be blown off from the suction region into the suction gas path against the suction gas flowing downstream.     The screw compressor according to claim 16, wherein the baffle is disposed upstream of the motor and downstream of the position where the suction gas flows into the compressor housing.     The baffle is disposed so as to block oil blown in the reverse direction in the suction gas path and change its direction so as to go to the position of the suction region where the oil tends to accumulate. The screw compressor according to claim 18.     18. The screw compressor according to claim 17, wherein the baffle is disposed downstream of the motor and substantially in the suction area.     The baffle is disposed generally at the outlet of the intake gas path, and is arranged to block and change the direction of oil that reaches the vicinity of the outlet of the path away from the path. 21. The screw compressor according to claim 20, wherein oil is at least partially prevented from flowing into a certain position of the suction area that is easily blown away in the reverse direction via the suction path.     The baffle is disposed upstream of the motor and downstream of the position where the suction gas flows into the compressor housing, and is disposed downstream of the motor and generally in the suction region. The screw compressor according to claim 17, further comprising a baffle.     The first baffle is disposed so as to block the oil blown in the reverse direction through the suction gas path and change the direction so that the oil returns to the position in the suction area where the oil is likely to accumulate. The second baffle is formed so as to prevent oil from flowing to a position in the suction region where the oil easily flows back through the suction gas passage. Item 23. The screw compressor according to Item 22.     The motor housing defines at least one oil return path, and the oil blocked and redirected by the first baffle is routed through the oil return path into the suction area. Item 24. The screw compressor according to Item 23. The refrigeration chiller according to any one of claims 1 to 14 , wherein the oil chiller is prevented from flowing back from the compressor of the chiller chiller to the evaporator ,
A method comprising: preventing at least one baffle disposed upstream of the working chamber from flowing back to the refrigerant from the position where the oil tends to accumulate . The refrigeration chiller according to any one of claims 1 to 14, wherein the drive motor is used in a refrigeration chiller compressor.
Sending refrigerant gas downstream from the evaporator to the compressor;
By the steps, that the oil flowing refrigerant gas to the Tama Riyasui position and around the drive motor disposed upstream of said working chamber to cool the motor before said gas enters the working chamber how it said.

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